Solvent refining of wax-containing mixtures



Sept 14, 1954 E. w. CLARKE 2,689,205 SOLVENT REFINING 0F WAX-CONTAINING MIXTURES Filed Feb 25, 1951 INVENTOR. Bd 'ar W Clary/E:

dzarney Patented Sept. 14, 1954 SOLVENT REFINING OF WAX-CONTAINING MIXTURES Edgar W. Clarke, Laurel Springs, N. J., assignor to The Atlantic Refining Company, Philadelphia, Pa., a corporation of Pennsylvania Application February 23, 1951, Serial No. 212,288

The portion of the term of the patent subsequent to July 1'7, 1968, has been disclaimed and dedicated to the public 2 Claims. 1

The present invention relates to the treatment of oily waxes, and more particularly to the separation of wax-containing mixtures into fractions of higher and lower melting point.

This invention is especially applicable to the deoiling of hydrocarbon waxes containing not more than 70% of oil, and to the separation of wax mixtures of low oil content into fractions of different melting point.

This applicable is a continuation-in-part of copending application Serial No. 779,922, filed October 15, 1947, now U. S. Patent No. 2,561,096, and entitled Solvent Refining of Wax-Containing Mixtures.

In accordance with the invention, a waxcontaining mixture is separated into fractions of higher and lower melting point by admixing the wax-containing mixture with phenol as the selective solvent at a temperature above the cloud point of the admixture, cooling the admixture to a temperature below the cloud point such that two immiscible liquid phases are formed, one phase comprising a major portion of the higher melting wax in the form of finely divided particles suspended in a minor portion of the solvent, and the second phase comprising a major portion of the solvent containing dissolved lower melting wax, oil, and color bodies, separating the phases from one another, and removing the solvent from each. The quantity of solvent employed will usually range from 3 to 5 volumes per volume of wax-containing mixture to be treated, although in some cases as little as 1.5 volumes of solvent may be used. The cloud point will depend upon the nature of the wax-containing mixture, as well as upon the composition and volume of solvent used. The temperature of the initial heating must be above the cloud point, and may be above the miscibility temperature of the admixture. The cooling is preferably carried to a temperature between 1 F. and 5 F. below the cloud point in order that the higher melting wax may crystallize and form a suspension of finely divided particles in the immiscible liquid phase. This suspension is characterized as being non-filterable due to the fineness of the particles, but is fiowable. By efiecting separation of the wax at a temperature just below the cloud point, it is possible to avoid the use of filters and their attendant difliculties, on the one hand, and lilzewise to avoid the loss of selectivity of the solvent encountered in operating at a temperature above the cloud point but below miscibility temperature, on the other hand.

The process of the present invention may be applied in the refining, purification, or separation of wax stocks such as petroleum slack wax,

crude microcrystalline wax, paraffin waxes, petrolatum Wax, montan wax, ceresin, ozokerite, waxes from the destructive or non-destructive hydrogenation of mineral oil, synthetic hydrocarbon oil, shale oil, coal, and Waxes produced synthetically by the catalytic reaction of hydrocarbons, or waxes derived from the modified Fischer-Tropsch reaction of carbon monoxide and hydrogen.

The present invention may be further understood with reference to the accompanying drawing which represents diagrammatically a 2stage system suitable for carrying out the process.

Referring to the drawing, the wax stock in a molten condition is delivered from a storage ves sel I through valve-controlled pipe 2 to pipe 3 surrounded by a heating jacket 4 through which steam or other medium may be circulated to maintain the desired temperature. A hot solvent extract, phenol, containing lower melting Wax, oil, and possibly color bodies is simultaneously supplied to pipe 3 through pipe 5, the source of such solvent extract being described in detail hereinafter. In passing through jacketed pipe 3, the temperature of the wax stock and solvent extract is adjusted to a value above the cloud point of the admixture, and if desired, such temperature may be raised to or above the miscibility temperature of the admixture. The cloud point may be considered that temperature at which the higher melting wax appears as a suspension of finely divided solid particles, such particles being substantially non-filterable. In general, the temperature of the admixture at this stage should be from 5 F. to 30 F. above the cloud point. The admixture, at a temperature above its cloud point, is thoroughly agitated in its passage through pump 6, and is delivered by such pump to a cooling coil '1 or other suitable device for decreasing the temperature. Coil l is surrounded by jacket 8 through which brine, Water, or other cooling medium may be circulated. In passing through coil 2', the temperature or" the admixture is reduced to a value below its cloud point, preferably from 1 F. to 5 F. below the cloud point. As a result of the cooling, two immiscible liquid phases are formed, if not already in existence, the higher melting wax components being distributed as finely divided, non-filterable particles throughout the phases. This mixture is passed from coil 7 through valve-controlled pipe 9 into settling vessel It provided with a rotatable stirrer i I, which, if desired, may also function as a scraping device for loosening wax which may adhere to the walls of the vessel. In vessel It, the mixture is permitted to settle and stratify into two layers, the upper layer comprising for the most part the higher melting wax particles and a minor amount of solvent, for example, 5% to 20% by volume of the upper layer. The lower layer comprises the major portion of the solvent in which is dissolved the lower melting wax, oil, and color bodies (if present). A small amount of finely divided higher melting wax particles may also be entrained in the lower layer, due to failure to pass upwardly from the extract solution into the upper layer comprising the higher melting wax particles. The lower layer is then drawn from settling vessel I and is passed through valve-controlled pipe [2 into a fractionating or stripping tower I3 provided with a heating coil 14. In tower l3, the solvent is removed from the lower melting wax by vaporization, the solvent vapors being taken overhead through pipe l5, condensed in condenser l6, and delivered by valve-controlled pipe I! to valve-controlled pipe I8 for further use, as will be described. The lower melting wax is drawn from the bottom of tower l3 and passed by valve-controlled pipe 19 into storage vessel 20.

The upper layer contained in settling vessel l 0, comprising the major portion of the higher melting wax in the form of finely divided particles suspended in a minor portion of the solvent, is slowly agitated by rotation of stirrer II, and is drawn from vessel [0 through valve-controlled pipe I8, and is commingled therein with solvent from valve-controlled pipe II, as well as with solvent delivered by valve-controlled pipe 2|, the source of which will be hereinafter described. The resulting admixture of finely divided higher melting wax and solvent is passed through pipe 22 surrounded by heating jacket 23, and the temperature of the admixture is brought to a value above the cloud point, and if desired, above the miscibility temperature. The heated mixture is then delivered by pump 24, with thorough agitation, to cooling coil 25 surrounded by jacket 26 through which a cooling medium may be circulated. The temperature of the mixture is reduoed to a level a few degrees below its cloud point (1 F. to R), and the mixture is then delivered by valve-controlled pipe 21 to settling vessel 28 provided with stirrer 29. Herein, the immiscible liquid phases are permitted to settle and stratify and there is produced an upper layer comprising a major portion of the higher melting wax in the form of a fine suspension in a minor amount of solvent, the wax being relatively light colored and of much reduced oil content. The lower layer comprises the major portion of the solvent with minor amounts of lower melting wax, oil, and color bodies, if present. The lower layer is withdrawn from vessel 28 and is recycled by means of valve-controlled pipe 5 to pipe 3 for use as explained hereinbefore.

The upper layer contained in vessel 28 is slowly agitated by stirrer 29, and is passed by valvecontrolled pipe 30 to the fractionating or stripping tower 3|, provided with heating coil 32. In tower 3 i, the solvent is separated from the higher melting wax by distillation, the wax being withdrawn from the bottom of the tower via valvecontrolled pipe 33 and passed to storage vessel 34. The solvent is taken overhead as vapor through pipe 35, condensed in condenser 36, and delivered by valve-controlled pipe 2| to pipe 18 for further use as described hereinbefore.

While the invention has been particularly described with respect to the operation of a 2-stage system, it is obvious that it may likewise be carried out in a system of any described number of stages, depending upon the degree of separation of the wax-containing mixture required. Preference is had for a system containing from 3 to 5 stages in order to obtain the most effective separation of the higher and lower melting point waxes.

The present invention may be further illustrated by the following examples, which, however, are not to be construed as limiting the scope thereof.

(1) A slack wax of brown color having a melting point of 113 F. and an oil content of 43.1% by weight, was extracted with phenol in a 3-stage system operated in the manner described with reference to the system shown in the drawing. The volume ratio of phenol to wax stock was 4.5 to l. The extraction temperature was F. in the first stage and F. in the second and third stages. In the table which follows, a comparison is made between the properties of the charge stock together with the properties of the raflinate and extract phases from the process.

gigg Railinate Extract Percent Yield by Welght Melting Point, F 113.1 Percent Oil Content by Weight .3 Refractive Index at 176 F l.4415

olor Brown Firmness.. Nil il. Tackiness. Poor o Plasticity Too soft do Fiber Leng h Long Short Flexibility Poor Moderate" 233 Rafiinate Extract Percent Yield by Weight. 100 72 28. Melting P0int, F 113.1 1 118.0 104.5 Percent Oil Content by 24.2 18.3 39.4.

eight. Refractive Index at 176 F.

Tackiness. Plasticity Fiber Length Short... Long Short Flexibility Nil Good..

(3) The same slack wax used in Example 2 above was utilized in this experiment in a single stage extraction at a temperature of 119 F. with phenol as the solvent. The ratio of solvent to wax stock was 2.30 to 1. In the table which follows, a comparison is made between the properties of the charge stock together with the properties of the raifinate and extract phases from the process.

2255 Raffinate Extract Percent Yield by Weight- 100 85.1 Melting Point, F 113. 116.3 Percent Oil Content by 24.2" 20.3

Weight. Refractive Index at 176 F.. 1.43625 1.43245... 1.43700.

Color Brown. White... Brown.

I claim:

1. The method of separating a wax-containing mixture into fractions of higher and lower melting point, which comprises admixing said waxcontaining mixture with from 3 to 5 volumes of phenol at a temperature above the cloud point of the admixture, cooling the admixture to a temperature of 1 F. to 5 F. below the cloud point such that two immiscible liquid phases are formed, one phase comprising a major portion of the higher melting wax in the form of finely divided, unfilterable particles suspended in a minor portion of the phenol, and the second phase comprising a major portion of the phenol containing dissolved lower melting wax, oil, and color bodies, separating the phases from one another, and removing the phenol from each.

2. The method of separating a wax-containing mixture into fractions of higher and lower melting point, which comprises admixing said waxcontaining mixture with from 3 to 5 volumes of phenol at a temperature of 5 F. to 30 F. above Number Name Date 2,017,432 Bahlke Oct. 15, 1935 2,063,369 Diggs et al Dec. 8, 1936 2,126,493 McKittrick et a1 Aug. 9, 1938 2,191,136 Tijmstra Feb. 20, 1940 2,302,434 Dons et al Nov. 17, 1942 2,561,096 Clarke July 17, 1951 the cloud point of the admixture, cooling the admixture to a temperature of 1 F. to 5 F. below the cloud point such that two immiscible liquid phases are formed, one phase comprising a major portion of the higher melting wax in the form of finely divided, unfilterable particles suspended in a minor portion of the phenol, and the second phase comprising a major portion of the phenol containing dissolved lower melting wax, oil, and color bodies, separating the phases from one another, and removing the phenol from each.

References Cited in the file of this patent UNITED STATES PATENTS 

1. THE METHOD OF SEPARATING A WAX-CONTAINING MIXTURE INTO FRACTIONS OF HIGHER AND LOWER MELTING POINT, WHICH COMPRISES ADMIXING SAID WAXCONTAINING MIXTURE WITH FROM 3 TO 5 VOLUMES OF PHENOL AT A TEMPERATURE ABOVE THE CLOUD POINT OF THE ADMIDTURE, COOLING THE ADMIXTURE TO A TEMPERATURE OF 1* F. TO 5* F. BELOW THE CLOUD POINT SUCH THAT TWO IMMISCIBLE LIQUID PHASES ARE FORMED, ONE PHASE COMPRISING A MAJOR PORTION OF THE HIGHER MELTING WAX IN THE FORM OF FINELY DIVIDED, UNFILTERABLE PARTICLES SUSPENDED IN A MINOR PORTION OF THE PHENOL, AND THE SECOND PHASE COMPRISING A MAJOR PORTION OF THE PHENOL CONTAINING DISSOLVED LOWER MELTING WAX, OIL, AND COLOR BODIES, SEPARATING THE PHASES FROM ONE ANOTHER, AND REMOVING THE PHENOL FROM EACH. 